The present invention relates, in general, to disc brakes and, more particularly, this invention relates to an indicator of brake disc wear using shallow holes provided in the casting of the brake disc.
Prior to the development of the present invention, the normal industry practice for indicating wear on a brake disc, or rotor, utilized a chamfer located on the outer diameter of the braking surface. The dimensional thickness of the chamfer shows brake disc wear and, thus, shows the remaining brake disc material allowed for continued disc use. When the brake disc is worn sufficiently to substantially eliminate the chamfer, the brake disc is condemned and replaced.
There is a problem with this prior art type chamfer thickness approach in that these brake discs will typically exhibit wear in a concave manner (as can best be seen in FIG. 2 in the present application) so that such concave wear can allow the brake disc to be worn both to and beyond the minimum allowed before the chamfer disappears. This requires the user of the disc to measure the depth of the concave section and subtract such section from the remaining chamfer, which, of course, takes time and decreases the value of the chamfer to the user.
The above-described problem is substantially solved, according to the present invention, by eliminating the chamfer altogether and casting wear indicating holes in the body of the brake disc. These wear indicating holes are located at the rear of braking surfaces such that these holes are obscured by the disc material subject to wear. When the material of the disc in front of the holes is worn to the extent that the holes appear at the front braking faces of the disc, the disc is considered worn to the extent that it is replaced. These wear indicating holes are cast into the body portion of the disc when the disc is manufactured, i.e., cast, and a plurality of the wear indicating holes can be circularly spaced and spread radially between the center hub and the periphery of the disc.
It is, therefore, a primary object of the present invention to provide wear indicating holes in the body of a brake disc at specific positions located at the rear of and thus behind the braking disc surface and associated disc material such that when the front braking faces of the disc are worn to the extent that the holes appear, the disc is replaced with a new unworn disc.
Another object of the present invention is to provide a brake disc in which the wear indicating holes are normally cast with bottom surfaces that are rounded to reduce the occurence of stress risers.
A further object of the present invention is to provide a brake disc in which the wear indicating holes can be provided with a conical, or varying diameter, shape to indicate a partially worn disc and thereby allow a predetermined amount of time at normal usage to schedule disc replacement.
Still another object of the present invention is to provide a brake disc in which a first appearance of the wear indicating hole from the front side of the brake disc may not require the immediate replacement of the disc but will provide the user/customer a period of time to schedule disc replacement.
In addition to the objects and advantages of the present invention described above, various other objects and advantages of the invention will become more readily apparent to those persons skilled in the relevant art from the following much more detailed description of the invention, particularly, when such description is taken in conjunction with the attached drawing Figures and with the appended claims.